All components of Zaku II F2 EFSF Ver.Only the arms are the components without inner frames it seems. ^^;

More images of this partial-skeletal form (^^;) of MG Zaku II F2 EFSF Ver.:

Closeups on the details:

For a near one-decade old MG kit, the inner frame is quite impressive in my opinion. ^^ The details are very well designed. Some of them even made it to MG Zaku II Ver. 2.0 I think - the backpack's and part of the legs' inner frame details look very similar to the same components on that successor MG. ^^ Still, MG Zaku II Ver. 2.0 is miles beyond this kit. Not only does it feature a complete inner frame, including parts for the arms, a "cage" for the left shoulder armor plus many other components, its articulation design is way better as well. With Zaku II F2 EFSF Ver., you can still feel that the inner frame is mainly just for extra display purpose. The entire frame still looks very thin, hollow and "incomplete" to me. ^^;

A look at the shoulder joints' expansion now that the arms are assembled onto the inner frame:

The articulation is already pretty good without the pull-out gimmick, with the latter, the shoulder joint can do a near 180-degree upward swing. ^^ It's very impressive, but there's no need for such a huge articulation range really, since the shoulder armors on both arms would have collided with the head long before the bend is achieved. XD

Interestingly, the only other Gunpla I remember with similar joint design is Perfect Grade Gundam Mk. II, which was released in November 2001, less than a year before this MG came out. Master Grade Zeong featured similar joint design, but that was meant more as a compliment to the shoulder blocks' expansion gimmick in my opinion.

Advances in joint design was probably the reason why it wasn't utilized more on other kits, but it's very amazing to see how fast the design got replaced by newer type nonetheless. ^^